1. Field of the Invention
The present invention relates to power generation and more specifically relates to a solid-fueled power system which provides for complete carbon dioxide recovery and methods therefor.
2. Brief Description of the Prior Art
The growing concern regarding global climate change has prompted the world community to implement strategies for reducing the emission of so-called greenhouse gases. Carbon dioxide (CO.sub.2), which is produced by all systems that burn fossil fuels, is the most important species in this category. Emissions of carbon dioxide are particularly high for systems which use solid fuels such as coal. One solution for addressing this problem is to increase the energy conversion efficiency of fossil-fueled power plants. Another longer-term strategy which is receiving serious support from the international community, in general, and the U.S. Department of Energy, in particular, consists of sequestering and capturing the CO.sub.2 emitted from fossil fueled systems (hereinafter referred to as "CO.sub.2 capture"). CO.sub.2 capture is typically accomplished by treating the exhaust stream to separate out the CO.sub.2 component in a form suitable for removal and storage. In conventional systems, this is difficult to achieve because of the low concentration of CO.sub.2 compared to the other components (namely, nitrogen) in the exhaust. The result is a process that is both costly and energy intensive.
U.S. Pat. No. 5,724,805 to Golomb et al. discloses a power plant including an air separation unit arranged to separate oxygen from air and produce a stream of oxygen and a gas turbine for combusting a fuel, such as natural gas, in the presence of the oxygen. The power plant includes a carbon dioxide removal unit arranged to recover carbon dioxide gas from the exhaust gas, recycle a portion of the recovered carbon dioxide gas for passage through the gas turbine, and liquefy the remainder of the recovered carbon dioxide gas for removal from the plant. As disclosed in the '805 patent, a portion of the CO.sub.2 gas leaving the turbine is recovered from the CO.sub.2 /H.sub.2 O exhaust stream, recycled to the inlet of the compressor and recompressed. The compression of the CO.sub.2 gas prior to recycling requires a significant amount of energy, thereby minimizing the overall efficiency of the system.
Thus, there is a need for a more efficient solid-fueled cogeneration system which overcomes the above-described problems.